This invention relates to an electronic identification system having a tag which is attached to a person or object for identification purposes. The tag can in a first mode when asked to identify by an interrogation signal communicate via radio frequency with fixed locations to identify the tag, such as at portals, for access control to secured areas, and in a second mode the tag can communicate as a beacon with fixed equipment to provide for identification and corresponding position or tracking of the tag.
The protection and tracking of personnel and property in high security areas continues to be a vexing problem. Airports, government facilities, and industrial sites are increasingly concerned with securing large areas for controlled access. Often times the very areas in which it is desired to restrict access also require a large number of authorized occupants to gain legitimate access to work areas. Use of guards and screening devices at entrances needs to be complemented by continuous monitoring of personnel once they are on the premises. The use of television cameras and monitors as a solution to this problem suffers from the limitations of human fatigue and the lack of automation to track and distinguish authorized from unauthorized occupants in a secure area. Advanced technology including concepts using laser and infrared signals to track people or objects moving in secured areas provide some help. The need still exists to distinguish authorized from unauthorized persons or objects. While optical means have been suggested for accomplishing such distinguishing of authority, optical means are limited by line-of-sight operation. In addition to tracking and identification of people or objects in a secured area, it is also desirable to restrict entrance into the secured area to those who have proper identity. Access cards and electronic portal admission devices are known and can provide an initial distinguishing of authorized and unauthorized personnel or objects upon access.
An airport location is typical of the complex needs of a modern security site. Portals into the high security runway and baggage areas can be either manned or provided with optical or electronic identity card readers so as to provide a first line of defense against unauthorized entrance into the larger expanse of the runway and baggage areas. Such single line defense is usually considered inadequate for security purposes, and a further security network will be provided. Infrared, optical, or laser scanning systems can be used to identify persons moving within the wide security area, such as the airfield and baggage areas. Unfortunately in such areas activity of authorized persons cannot be distinguished from the movement of unauthorized persons by such scanning systems. There is a need to identify and distinguish authorized from unauthorized persons in a wide area after admission to the area has been gained through some type of portal security system. If authorized persons can be identified and their positions known, then the positions and locations of the authorized personnel can be removed from the data set of the movement detectors and appropriate security action can be taken with regard to the remaining personnel or objects detected.
Reliable identification is also desired in a warehousing situation where it is desired to identify certain commodities when they enter at a warehouse portal and later to identify the position and identity of commodities in a wide area, such as storage or work areas.
In both the security and commodities identification applications it is desirable that the identification system provide for reliability, low cost, relatively long life of batteries or other power supplies, and small size so as to be convenient in use.